According to U.S. News & World Report, two new studies show that people associate anger with male faces and happiness with female ones. When subjects were shown androgynous faces that looked angry, they were more likely to identify them as male. But if the faces looked happy or fearful, people were more likely to label them as female. And in another experiment, subjects were slower to identify faces as female if the faces looked pissed off. Says psychologist Ursula Hess, "The present research shows that the association between anger and men and happiness and women is so strong that it can influence the decisions about the gender of another person when that person is viewed briefly."

In another study, researchers gave women testosterone pills and studied how they played a cooperation-based game. The game involved giving one woman $10 and instructing her to choose an amount to offer her partner. If the partner turned down the offer, neither got money. Women who received testosterone were no less generous than their peers — unless they were told they'd gotten the hormone. Those who knew they'd gotten testosterone "stood out with their conspicuously unfair offers," wrote the study authors. Lead author Ernst Fehr says that when asked about how they thought testosterone would affect them, the subjects said things like, "Oh, testosterone would make me more egotistic, more risk-taking and more aggressive." In other words, they thought testosterone would make them drive a harder bargain, and so they did just that, even though the testosterone alone might have had no effect.

What's interesting about these studies is that they show how deeply ingrained our perceptions of masculinity and femininity are — and, in the case of the bargaining study, how these perceptions may be even stronger than reality. Are women actually happier than men? Are men more angry? Probably not — but we may be socialized to express these emotions more freely, with the result that they become associated with gender. The result looks a lot like a feedback loop: girls are told it's not feminine to get mad, so they avoid making mad faces, and so people begin to think that anger is for men, and the cycle begins all over again. Similarly, if women learn that aggression is "male," they may not behave aggressively (except when hopped up on testosterone), further reinforcing this stereotype. The finding that this stereotype outstrips the actual effects of testosterone underscores the fact that gender differences are problematic, and that we shouldn't be too quick to assume that any difference in behavior has a biological basis. As Michael Naef, co-author of the testosterone study, says, "In a society where qualities and manners of behavior are increasingly traced to biological causes...this should make us sit up and take notice."